Vacuum system for mass spectrometer

Abstract

The invention discloses a vacuum system for a mass spectrometer. The vacuum system includes a first vacuum region, a second vacuum region, a vacuum interlock connected to the first vacuum region by a first valve and to the second vacuum region by a second valve, a first pump connected to the first vacuum region and the second vacuum region, a second pump connected to the second vacuum region, a pressure sensor configured to determine a pressure within the second vacuum region, and a controller configured to adjust a position of the second valve in response to the pressure within the second vacuum region. The vacuum interlock device is configured to receive a sample. The first pump is configured to reduce pressure within the first vacuum region and discharge air to the second vacuum region. The second pump is configured to reduce pressure within the vacuum interlock. The controller is configured to prevent pressure fluctuations in the second vacuum region.

Description

Technical Field

[0001] The present disclosure relates to mass spectrometers. More specifically, the present disclosure relates to a vacuum system and an associated control system for evacuating a vacuum interlock device in a mass spectrometer. Background Art

[0002] Certain markets using mass spectrometers focus on processing as large a number of samples as possible through the instrument. In operations involving high-volume sample processing, a mass spectrometer may require a significant amount of time and energy to operate the vacuum system. This can result in time-intensive and cost-intensive processing of samples through the instrument. Thus, there is an opportunity to improve the vacuum system to reduce the time required to complete a vacuum system operation cycle associated with sample processing or performing maintenance, and to improve vacuum system components to reduce energy requirements. Summary of the Invention

[0003] In one example of an embodiment, a vacuum system for a mass spectrometer includes a first vacuum region, a second vacuum region, a vacuum interlock device fluidly connected to the first vacuum region through a first valve and fluidly connected to the second vacuum region through a second valve, a first pump fluidly connected to the first vacuum region and the second vacuum region, a second pump fluidly connected to the second vacuum region, a pressure sensor configured to determine the pressure within the second vacuum region, and a controller configured to incrementally adjust the position of the second valve in response to the pressure within the second vacuum region. The vacuum interlock device is configured to receive a sample. The first pump is configured to reduce the pressure within the first vacuum region and expel air into the second vacuum region. The second pump is configured to reduce the pressure within the vacuum interlock device. The controller is configured to prevent pressure fluctuations in the second vacuum region.

[0004] In another example of an embodiment, a method of evacuating a vacuum interlock device in a vacuum system of a mass spectrometer, the vacuum system including a first vacuum region fluidly connected to the vacuum interlock device through a first valve, a second vacuum region fluidly connected to the vacuum interlock device through a second valve, a first pump that reduces the pressure within the first vacuum region, and a second pump that reduces the pressure within the second vacuum region. The method includes a first operation cycle that includes closing the first valve and the second valve to fluidly isolate the vacuum interlock device from the first vacuum region and the second vacuum region; measuring the pressure within the second vacuum region; incrementally opening the second valve to reduce the pressure within the vacuum interlock device, the second valve being incrementally opened in response to the pressure within the second vacuum region; closing the second valve in response to the vacuum interlock device reaching an operating pressure; and opening the first valve in response to the vacuum interlock device reaching an operating pressure to facilitate transferring at least one of a sample, an ion source cylinder, or a source plug from the vacuum interlock device to the first vacuum region.

[0005] Other aspects of the invention will become apparent in view of the detailed description and the drawings. Description of the Drawings

[0006] Figure 1 is a schematic diagram of a mass spectrometer including an embodiment of a vacuum system.

[0007] Figure 2 is to provide Figure 1 an example of the operating steps of a mass spectrometer in the form of a flowchart.

[0008] Figure 3 is a schematic diagram of a part of a mass spectrometer including an alternative embodiment of a vacuum system.

[0009] Figure 4 is Figure 3 a schematic diagram of a mass spectrometer and an associated vacuum system.

[0010] Figure 5 is to provide Figure 3 an example of the operating steps of a mass spectrometer in the form of a flowchart.

[0011] Figure 6 is Figure 5 a flowchart of an evacuation sequence implemented at step 312 of the operating steps of

[0012] Before explaining any embodiment of the present invention in detail, it should be understood that the present invention is not limited in its application to the details of the construction and arrangement of components set forth in the following description or shown in the following drawings. The present invention is capable of having other embodiments and of being practiced or carried out in various ways. Detailed Description

[0013] The mass spectrometer systems and methods described herein reduce the turnaround time, pump power consumption, and wear and tear on the pumps during the replacement of parts (e.g., samples or maintenance parts) from the atmosphere to the high-vacuum region of the mass spectrometer by carefully controlling the pressure leak between the vacuum regions using a controller (e.g., by the open / closed state of a control valve). The replacement of parts typically occurs through a vacuum interlock chamber that starts at atmospheric pressure. By ensuring that all vacuum pumps operate within their optimal differential pressure range and pumping speed range, carefully controlling the pressure release from the vacuum interlock chamber using a controller can reduce the turnaround time and reduce pump wear and tear. Carefully controlling the pressure release using a controller can also enable the use of smaller vacuum pumps with lower power consumption because these smaller pumps can conveniently exhaust the reduced gas flow from the controlled release.

[0014] When moving a component from outside the vacuum system of a mass spectrometer to inside the system, the vacuum interlock chamber at atmospheric pressure cannot be directly connected to the high-vacuum region because a sudden influx of high pressure into a high-vacuum pump (such as a turbopump) has the potential to damage the high-vacuum pump. Therefore, the vacuum interlock chamber must be evacuated before it is fluidly connected to the high-vacuum chamber. In some conventional systems, a roughing pump that supports the high-vacuum pump is used to evacuate the vacuum interlock chamber. This arrangement has potential drawbacks because the influx of high-pressure air from the vacuum interlock chamber into the roughing pump (and thus into the outlet or return of the high-vacuum pump) can raise the pressure at the outlet of the high-vacuum pump. If the pressure at the outlet of the high-vacuum pump becomes too high, the high-vacuum pump may become contaminated or overheated, or the vacuum level in the high-vacuum region may be impaired. The mass spectrometer systems and methods described herein overcome these problems by using a controller to carefully control the release of air from the vacuum interlock device into the roughing pump to prevent pressure spikes and ensure that the air flow rate from the vacuum interlock device to the roughing pump remains within the capacity of the roughing pump to handle. In the various examples described herein, the controller can control the release of air from the vacuum interlock device based on real-time pressure measurements, preset values retrieved from memory, or historical measurements stored in memory.

[0015] Figure 1 An example of an embodiment of a mass spectrometer 10 is shown. The mass spectrometer 10 includes a vacuum system 12. The vacuum system 12 is in fluid communication with an ion source 13. The ion source 13 is in fluid communication with a mass analyzer 14. These known components of the mass spectrometer 10 within the vacuum system 12 are represented by box 15. The vacuum system 12 includes a first pump 16 (also referred to as a high-vacuum pump 16) that is fluidly connected to a first vacuum region 18 and a second vacuum region 22. The first vacuum region 18 may also be referred to as the high-vacuum region 18, while the second vacuum region 22 may also be referred to as the low-vacuum region 22 (or roughing region 22). The high-vacuum pump 16 is configured to create a first vacuum (e.g., a pressure less than 10 -4 torr, a pressure less than 3×10 -5 torr, etc.) within the high-vacuum region 18. The high-vacuum pump 16 is also configured to expel gas into the low-vacuum region 22. The high-vacuum pump 16 can be any suitable vacuum pump for creating a target vacuum in the high-vacuum region 18, including but not limited to multi-stage turbomolecular pumps, diffusion pumps, etc.

[0016] The second pump 26 (also referred to as a roughing pump 26 or a low vacuum pump 26) is fluidly connected to the low vacuum region 22. The roughing pump 26 is configured to evacuate exhaust gas from the high vacuum pump 16. The roughing pump 26 generates a second vacuum (e.g., a pressure less than 5 Torr, a pressure less than 200 mTorr, etc.) within the low vacuum region 22. The second vacuum is a lower vacuum than the first vacuum (i.e., the second vacuum has a higher pressure than the first vacuum). The roughing pump 26 includes an exhaust valve 28. The roughing pump 26 is configured to discharge air from the low vacuum region 22 to the surrounding atmosphere. A pressure sensor 30 is in communication with the low vacuum region 22. The pressure sensor 30 is configured to detect the pressure (also referred to as back pressure) within the low vacuum region 22.

[0017] The vacuum interlock device 34 is selectively fluidly connected to the high vacuum region 18 through a first valve 38 (also referred to as the high vacuum valve 38). The high vacuum valve 38 can be, for example, a ball valve, a gate valve, or any other suitable valve. The high vacuum valve 38 can be opened to, for example, allow a sample 40 (or a mechanical component 40) to enter the high vacuum region 18. The sample 40 can be an analytical sample to be measured. The mechanical component 40 can be a barrel of the ion source 13, a source plug, or any other component of the mass spectrometer 10 that can be replaced to facilitate maintenance operations. For example, the high vacuum valve 38 can be opened to replace the barrel of the ion source 13. The barrel of the ion source 13 can be replaced to remove dirty (used) components of the ion source 13 and insert clean (new) components of the ion source 13. The barrel of the ion source 13 can also be replaced to change the ionization volume to allow different ionization techniques (e.g., electron ionization, chemical ionization, etc.). The source plug can be replaced to, for example, seal the delivery line of a gas chromatograph to allow replacement of the column of the gas chromatograph. The sample 40 (or the mechanical component 40) can be positioned within a tool 42 (also referred to as the source replacement tool 42 or the sample probe 42). The tool 42 is configured to be coupled to the vacuum interlock device 34. The tool 42 is selectively extendable. When the high vacuum valve 38 is open, the tool 42 can extend to insert the sample 40 into the high vacuum region 18. The vacuum interlock device 34 is selectively fluidly connected to the low vacuum region 22 through a second valve 46 (also referred to as the evacuation valve 46). The evacuation valve 46 can be, for example, a solenoid valve, a proportional solenoid valve, a piston slide valve, a lift valve, or any other suitable valve. A first restrictor 50 is positioned between the vacuum interlock device 34 and the evacuation valve 46. The first restrictor 50 is configured to limit the flow of fluid (e.g., air, water vapor, etc.) between the vacuum interlock device 34 and the evacuation valve 46. An expansion volume 54 is positioned between the high vacuum valve 38 and the low vacuum region 22. The expansion volume 54 is configured to provide an increased evacuation volume for the incoming fluid to expand into in response to an increase in the airflow from the vacuum interlock device 34 to the expansion volume 54 and to reduce pressure surges, which will be discussed in further detail below. A second restrictor 58 is positioned between the expansion volume 54 and the low vacuum region 22. The second restrictor 58 is configured to limit the flow of fluid between the expansion volume 54 and the low vacuum region 22. The first restrictor 50 and the second restrictor 58 can be, for example, fixed gas restrictors.

[0018] Continue to refer to Figure 1, the controller 62 is configured to communicate with one or more components of the vacuum system 12. For example, the controller 62 communicates with the first valve 38 and the second valve 46. The controller 62 is configured to detect the position of the valve 38 and can open and / or close each of the first valve 38 and the second valve 46. In some examples, the controller 62 can be used to send a signal to a user (i.e., an audio signal or a visual signal such as through a graphical interface) to manually open or close the valve 38 if the valve 38 is not electronically controlled. As another example, the controller 62 communicates with the pressure sensor 30 and is configured to receive the pressure measurement in the low vacuum region 22 detected by the pressure sensor 30. In some examples, the controller 62 is configured to read the measurement from the pressure sensor 30 at a rate within the range of 5 - 10 Hertz. The controller 62 can include a memory 66 (also referred to as a database 66). The controller 62 is configured to store the measured data in the database 66. In some examples of the embodiments, the database 66 can be external to the controller 62 and is configured to communicate remotely with the controller 62.

[0019] Now referring to Figure 2 , a process 100 for operating a mass spectrometer is shown. The process 100 utilizes a mass spectrometer 10 having a vacuum system 12. The process 100 includes a plurality of instructions depicted as steps in a flowchart form. The process 100 begins at step 104, where the vacuum interlock device 34 is fluidly isolated from the high vacuum region 18, the low vacuum region 22, and the expansion volume 54. The vacuum interlock device 34 is isolated by closing the high vacuum valve 38 and the evacuation valve 46. The vacuum interlock device 34 is isolated to prevent damage to the high vacuum pump 16. Damage to the high vacuum pump 16 can occur if air in the vacuum interlock device 34 rapidly and uncontrollably flows into the low vacuum region 22.

[0020] Next, at step 108, the sample 40 is introduced into the vacuum interlock device 34. Alternatively, step 108 can include the mechanical assembly 40 being introduced into the vacuum interlock device 34, which will be discussed in further detail below. If step 108 occurs after the sample 40 has been previously tested and the tool 42 is coupled to the vacuum interlock device 34, then the tool 42, along with the previously tested sample 40, is removed from the vacuum interlock device 34. The removal of the tool 42 fills the vacuum interlock device 34 with external air at atmospheric pressure. When filled with air at atmospheric pressure, the vacuum interlock device 34 can be said to be at the starting pressure. Once the tool 42 is removed, the tool 42 can be cleaned and any remaining material from the previously tested sample 40 can be removed. The tool 42 can then be reused by inserting a new sample 40 to be ionized or replaced into the tool 42. Alternatively or additionally, a second tool 42 can carry the new sample 40 to be ionized or replaced. The tool 42 carrying the new sample 40 is then coupled to the vacuum interlock device 34. Coupling the tool 42 to the vacuum interlock device 34 seals the vacuum interlock device 34 from the external air. The vacuum interlock device 34 now includes the new sample 40 carried by the tool 42. Then, the vacuum interlock device 34 is sealed at the starting pressure in response to the insertion of the tool 42.

[0021] Next, at step 112, air is evacuated from the vacuum interlock device 34 until the vacuum interlock device 34 reaches the operating pressure. The pressure in the vacuum interlock device 34 is reduced to facilitate the transfer of the sample 40 from the vacuum interlock device 34 to the high vacuum region 18. The air is evacuated from the vacuum interlock device 34 from the atmospheric starting pressure to a reduced target pressure (also referred to as the operating pressure). The target pressure is not as low as the first vacuum in the high vacuum region 18. However, the target pressure is low enough so as not to create a harmful pressure differential between the vacuum interlock device 34 and the high vacuum region 18 (i.e., a pressure differential that would damage the high vacuum pump 16 or cause a delay in evacuating the low vacuum interlock device 34). The target pressure can be a predetermined pressure value. The controller 62 can detect the pressure from the pressure sensor 30 to determine if the vacuum interlock device 34 is at the target pressure. For example, once the pressure within the low vacuum region 22 has stabilized, the controller 62 can determine that the vacuum interlock device 34 is at the target pressure.

[0022] The vacuum interlock device 34 is evacuated by opening the vent valve 46. Opening the vent valve 46 can cause a sudden burst of air at atmospheric pressure (also known as high-pressure air) to leave the vacuum interlock device 34 through the vent valve 46. The expansion volume 54 is configured to provide an increased evacuation volume for the incoming fluid to expand volumetrically, thereby preventing a pressure differential between the expansion volume 54 and the low-vacuum region 22. The air pressure in the expansion volume 54 is configured to be effectively reduced by the roughing pump 26. The first restrictor 50 is configured to reduce the flow of high-pressure air into the expansion volume 54. The second restrictor 58 is configured to reduce the flow of high-pressure air from the expansion volume 54 into the low-vacuum region 22. The first restrictor 50 and the second restrictor 58 can thus suppress the impact of a sudden pressure change (by introducing a certain volume of atmospheric-pressure air into the low-vacuum region 22) on the roughing pump 26 and the high-vacuum pump 16. The roughing pump 26 operates to reduce the pressure within the low-vacuum region 22.

[0023] It should be understood that the high-vacuum pump 16 can be damaged by a significant pressure differential between the vacuum interlock device 34 and the high-vacuum region 18. A small pressure differential can exist between the vacuum interlock device 34 and the high-vacuum region 18 such that once the high-vacuum valve 38 is opened, the gas within the vacuum interlock device 34 expands into the high-vacuum region 18 without damaging the high-vacuum pump 16. The small pressure differential can be caused by, for example, a pressure of 5 - 10 Torr within the vacuum interlock device 34. However, once the gas expands into the high-vacuum region 18, the pressure becomes equal to or less than the pressure within the low-vacuum region 22. A significant pressure differential can cause an uncontrolled rapid increase in the pressure within the high-vacuum region 18. An increase in the backpressure within the high-vacuum region 18 (also known as pressure fluctuations) can damage the high-vacuum pump 16. The high-vacuum pump 16 can also be damaged by a large pressure differential between the expansion volume 54 and the low-vacuum region 22. The pressure differential can cause an uncontrolled rapid increase in the backpressure within the low-vacuum region 22. This increase in the backpressure within the low-vacuum region 22 can damage the high-vacuum pump 16.

[0024] The vacuum interlock device 34 is evacuated until the pressure within the vacuum interlock device 34 reaches the target pressure. The time it takes for the roughing pump 26 to reduce the pressure within the vacuum interlock device 34 to the target pressure can be referred to as the evacuation time. In other words, the evacuation time is the amount of time it takes to reduce the pressure within the vacuum interlock device 34 from the starting pressure to the target pressure. It is desirable to minimize the evacuation time. The shorter the evacuation time within any given time period, the greater the number of samples 40 that can be tested by the mass spectrometer. Therefore, it is desirable for the roughing pump 26 to operate quickly so that the user can test more samples 40. Once the controller 62 determines that the vacuum interlock device 34 has reached the target pressure, the vent valve 46 is closed. At this point, the vacuum interlock device 34 is at the target pressure and is fluidly isolated from the remainder of the vacuum system 12.

[0025] Next, at step 116, once the vacuum interlock device 34 reaches the target pressure, the high vacuum valve 38 is opened. The vacuum interlock device 34 and the high vacuum valve 38 are now in fluid communication.

[0026] Next, at step 120, in response to the opening of the high vacuum valve 38, the sample 40 (or mechanical assembly 40) travels from the vacuum interlock device 34 to the high vacuum region 18. The tool 42 can be extended to place the sample 40 within the high vacuum region 18. The sample 40 can then be ionized, accelerated through the ion source 13, and tested.

[0027] After the testing of the sample, the process 100 of operating the mass spectrometer can be repeated with a different sample 40. The process 100 returns to step 104 where these steps are sequentially repeated. It should be understood that completing steps 104 to 120 can be referred to as an operating cycle. Thus, the process 100 with the first sample 40 can be referred to as the first operating cycle among a plurality of operating cycles. After the first operating cycle, the process 100 with the second sample 40 can be referred to as the second operating cycle among a plurality of operating cycles. After the second operating cycle, the process 100 with the third sample 40 can be referred to as the third operating cycle among a plurality of operating cycles. Additional operating cycles can follow the third operating cycle to define a plurality of cycles.

[0028] The process 100 describes the introduction and measurement of the sample 40. It can be understood that the process 100 can alternatively be performed to complete maintenance operations (e.g., replacing the cartridge, source plug, etc. of the ion source 13). The process 100 will include similar steps using the mechanical assembly 40 in place of the sample 40. For example, during the process of replacing the cartridge of the ion source 13, at step 108, the cartridge is introduced into the vacuum interlock device 34. At step 120, the cartridge replaces the old cartridge and then mates with the ion guide.

[0029] During the process 100 of operating the mass spectrometer, the high vacuum pump 16 and the roughing pump 26 can account for a significant portion of the operating energy. For example, the power consumption of the roughing pump 26 can be approximately 250 watts, and the power consumption of the entire mass spectrometer 10 can be 540 - 620 watts. Power consumption is required to quickly evacuate the vacuum interlock device 34. By using a smaller roughing pump that consumes less energy, there is an opportunity to reduce the energy consumption of the mass spectrometer 10. However, replacing the roughing pump 26 with a smaller one is not a simple replacement. Therefore, additional modifications to the mass spectrometer 10 and the associated vacuum system are required. Figures 3 - 4 An example of an embodiment of such a modified system is shown.

[0030] Figure 3 and Figure 4An alternative embodiment of a vacuum system 212 for use with a mass spectrometer 10 is shown. The vacuum system 212 includes components similar to those of the vacuum system 12, where like reference numerals identify like components. The vacuum system 212 includes a low-volume roughing pump 226 (also referred to as the second pump 226). The low-volume roughing pump 226 replaces the roughing pump 26. The low-volume roughing pump 226 can be, for example, a micro-vortex pump, a diaphragm pump, etc. The low-volume roughing pump 226 has a significantly lower power consumption than the roughing pump 26. For example, the low-volume roughing pump 226 can have a power consumption of about 30 watts - 50 watts. Thus, the low-volume roughing pump 226 can use approximately 12% - 20% of the power of the roughing pump 26. Relative to the roughing pump 26, the low-volume roughing pump 226 can also operate at a reduced audible sound. However, the low-volume roughing pump 226 also has a slower pumping speed than the roughing pump 26. Thus, if the low-volume roughing pump 226 is simply swapped for the roughing pump 26 in the vacuum system 12, the vacuum system 12 may not be able to operate at a sufficient speed to introduce a sample in a timely manner for ionization and analysis (e.g., in less than 30 seconds, in less than 15 seconds, etc.). Instead, if the vacuum system 12 uses a fixed gas first restrictor 50 and second restrictor 58 and an expansion volume 54, it may take a very long time (e.g., five minutes, 15 minutes, etc.) to evacuate the vacuum interlock 34. To use the low-volume roughing pump 226 and operate at a speed sufficient to cycle samples in a timely manner, the vacuum system 212 includes a proportional valve 246 (also referred to as the second valve 246 or the evacuation valve 246). The proportional valve 246 can be, for example, a solenoid valve. The proportional valve 246 replaces the evacuation valve 46. The proportional valve 246 is configured to be incrementally opened by a controller 62 to evacuate the vacuum interlock 34 to a target pressure. For example, the controller 62 can adjust the conductivity of the proportional valve 246 by adjusting the position of the proportional valve 246. The controller 62 is configured to minimize the evacuation time by optimizing the opening of the proportional valve 246 using data stored in a database 66, which will be discussed in further detail below. In some examples, the vacuum system 212 does not include a restrictor or an expansion volume 54 as in the vacuum system 12. By removing the expansion volume (i.e., minimizing the volume between the low-volume roughing pump 226 and the proportional valve 246) and the restrictor, the total volume pumped by the low-volume roughing pump 226 is reduced, and thus the total time to evacuate the vacuum interlock 34 can be reduced while harmful pressure surges or spikes can be avoided.

[0031] In other examples, the second valve 246 can be an on / off valve that the controller 62 operates in a fixed or variable duty cycle. For example, the controller 62 can cycle the valve 246 between "on" and "off" states in short bursts. In some examples, the effect of cycling the valve 246 is that the valve 246 does not fully open or fully close during the cycle period, and thus a proportional valve can be used to control the resulting gas flow through the valve 246 in a manner similar to that described above. The duty cycle operation of the valve 246 can have the advantage that a wider variety of nominal "fully open / fully closed" (i.e., non-proportional) valves can be used in conjunction with the system.

[0032] Specifically referring to Figure 4 , the high vacuum pump 14, the high vacuum valve 38, the low volume forepump 226, the proportional valve 246, and the pressure sensor 30 communicate with the controller 62. This communication is represented by dashed lines. This communication can be wired, wireless, or any suitable system for communication (e.g., radio, cellular, Bluetooth, etc.). The controller 62 is configured to receive operating data from at least one of the high vacuum pump 14, the high vacuum valve 38, the low volume forepump 226, the proportional valve 246, and / or the pressure sensor 30. The controller 62 can then save the received operating data in the database 66.

[0033] Referring to Figure 5 , an example of a process 300 for operating a mass spectrometer is shown. The process 300 utilizes a mass spectrometer 10 having a vacuum system 212. The process 300 includes a plurality of instructions or steps depicted in flowchart form. The process 300 begins at step 304, where the vacuum interlock device 34 is fluidly isolated from the high vacuum region 18 and the low vacuum region 22. The vacuum interlock device 34 is isolated by closing the high vacuum valve 38 and the proportional valve 246.

[0034] Next, at step 308, if the tool 42 is coupled to the vacuum interlock device 34, the tool 42 is removed from the vacuum interlock device 34. The removal of the tool 42 fills the vacuum interlock device 34 with external air at atmospheric pressure. Step 308 is the same as step 108. Thus, step 308 can include the same steps and features as those described in association with Figure 2 the step 108 shown.

[0035] Next, at step 312, air is evacuated from the vacuum interlock device 34 until the vacuum interlock device 34 reaches the operating pressure. Now referring to Figure 6 , step 312 is shown in more detail.

[0036] At step 316, the controller 62 increments the operation cycle counter C. The operation cycle counter C is a number associated with the corresponding operation cycle among a plurality of operation cycles. In the illustrated embodiment, the operation cycle counter C is incremented by one for each operation cycle, or C = C + 1. Thus, as an example, before the first operation cycle, the operation cycle counter C is incremented from a value of 0 to a value of 1 (C = 1, since 0 + 1 = 1). As another example, before the second operation cycle where C = 1, the operation cycle counter C is incremented from a value of 1 to a value of 2 (C = 2, since 1 + 1 = 2). In other examples of the embodiment, any suitable counter may be implemented to track the plurality of operation cycles.

[0037] Next, at step 320, the controller 62 uses the operation cycle counter C to determine whether there are sufficient detected pressure P, position V, operation cycle counter C, and time counter T values stored in the database 66 to correctly calculate the starting valve position V of the proportional valve 246 during the operation cycle. S The pressure sensor 30 is configured to detect the pressure P within the low vacuum region 22. The controller 62 is configured to detect the position V of the proportional valve 246. The controller 62 is also configured to determine the operation cycle counter C and the time counter T. The controller 62 is further configured to store the detected pressure P and position V values and the determined operation cycle counter C and time counter T values in the database 66. The controller 62 can then use the stored pressure P, position V, operation cycle counter C, and time counter T values to calculate the starting valve position V. S In other words, the controller 62 determines whether the proportional valve 246 should be opened to the calculated starting valve position V S or whether the proportional valve 246 should be opened incrementally. In the illustrated embodiment, the controller 62 determines whether the operation cycle counter C is greater than a predetermined number of cycles X. The predetermined number of cycles X represents the number of cycles required to store sufficient data suitable for calculating the starting valve position V. S As a non - limiting example, the predetermined number of cycles X may be equal to ten (X = 10). In this example of the embodiment, the controller 62 determines whether there have been more than ten cycles such that detected pressure P, proportional valve position V, and time counter T values for more than ten cycles have been stored in the database 66. In other embodiments, the predetermined value X may be any suitable number (e.g., one, five, fifteen, etc.). If the controller 62 determines that the answer is no, i.e., the mass spectrometer 10 has not operated for a sufficient number of operation cycles to store sufficient pressure P, position V, and time counter T values in the database 66, then the process proceeds to step 324.

[0038] Proceeding to step 324, the controller 62 incrementally opens the proportional valve 246 by an increment I. The increment I is equal to the adjustment amount of the position V of the proportional valve 246. Adjusting the position V of the proportional valve 246 incrementally by the increment I is configured to maintain the pressure in the low vacuum region 22 at or below a safe pressure. The low vacuum region 22 is fluidly connected to the high vacuum pump 16. Air entering the high vacuum pump 16 that is above the safe pressure may damage the high vacuum pump. In some embodiments, the controller 62 is configured to maintain the pressure in the low vacuum region 22 below the safe pressure multiplied by a safety factor. The safety factor can, for example, ensure that the pressure in the low vacuum region 22 does not approach the safe pressure. The safe pressure can be multiplied by the safety factor, and the product can be referred to as the adjusted safe pressure. When the position V of the proportional valve 246 is expressed as a percentage, the increment I can be equal to, for example, 1.0% when the proportional valve 246 is opened from zero percent (0.0%) to one percent (1.0%). In other embodiments, the increment I can be any suitable amount that safely facilitates the opening of the proportional valve 246 (e.g., 0.25%, 0.50%, 0.75%, 1.25%, 1.50%, etc.).

[0039] Next, at step 328, the controller 62 increments a time counter T. The time counter T can count time units throughout each operating cycle. In a non-limiting embodiment, the time counter T can be associated with the number of seconds and / or a fraction of a second that elapses during an associated operating cycle. For example, T can be equal to five (5) after five (5) seconds, ten (10) after ten (10) seconds, and so on. The time counter T can be reset for each operating cycle. Incrementing the time counter T indicates that a time unit has increased. In the illustrated embodiment, the time counter T is incremented by one (1) unit, or T = T + 1. In other embodiments, any counter suitable for tracking time units can be implemented. In other examples of embodiments, any suitable time unit can be utilized (e.g., seconds, half seconds, milliseconds, etc.).

[0040] Next, at step 332, the pressure P in the low vacuum region 22 is measured. The pressure sensor 30 measures the pressure P. The position V of the proportional valve 246 is also detected. The position V of the proportional valve 246 can be received from the proportional valve 246. In a non-limiting embodiment, the position V of the proportional valve 246 can be expressed as a percentage. For example, when the proportional valve 246 is fully closed, the position V can be 0%, when the proportional valve 246 is half open, the position V can be 50%, and when the proportional valve 246 is fully open, the position V can be 100%.

[0041] Next, at step 336, the controller 62 stores the detected pressure P, the detected proportional valve position V, the operating cycle counter C, and the time counter T values in the database 66. The measured pressure P and the measured position V can be indexed using the time counter T and the operating cycle counter C. In other words, for each value of the operating cycle counter C, there will be multiple time counter values T. The combination of a particular operating cycle counter value C and a time counter value T will correspond to a particular point in time during the operating cycle. Thus, at a particular time T, the pressure P and the valve position V are stored in the database 66. In one non-limiting embodiment, the operating cycle counter C can be used as the X-axis variable, and the time counter T can be used as the Y-axis variable. In this non-limiting embodiment, the unit of the pressure P is torr, the unit of the position V is the opening percentage of the proportional valve 246, and the format is listed as (P,V). For the first example data point, at C = 1, T = 1, after the proportional valve 246 is opened from 0% to 1.0% (i.e., an increment I of 1.0%), the pressure P is measured at 5 torr. Thus, the first example data point is (5,1) located at C = 1, T = 1.

[0042] At step 340, when high-pressure air enters the low-vacuum region 22, the low-capacity forepump 226 operates to initiate or re-establish the second vacuum level by reducing the pressure in the low-vacuum region 22. The low-capacity forepump 226 discharges the air that arrives through the valve 246 to the outside of the mass spectrometer 10 through the exhaust valve 28.

[0043] Next, at step 344, the controller 62 determines whether the pressure P in the low vacuum region 22 is less than the safety pressure (or adjusted safety pressure). If not, the pressure P in the low vacuum region 22 has not been sufficiently reduced by the low-capacity roughing pump 226, and the process then returns to step 328 to increment the time counter T. Steps 328 to 344 are then repeated until the detected pressure P in the low vacuum region 22 is less than the safety pressure (or adjusted safety pressure). As a non-limiting example, in an embodiment where the safety pressure is ten (10) Torr, during the operating cycle, the controller 62 incrementally opens the proportional valve 246 in increments I. The pressure in the low vacuum region 22 increases (the vacuum decreases). If the detected vacuum pressure is higher than the safety pressure, the low-capacity roughing pump 226 operates to reduce the pressure (or increase the vacuum) to ten (10) Torr or below ten (10) Torr before proceeding to step 348. In some embodiments, the controller 62 may decrease the valve position V. For example, if the pressure P in the low vacuum region 22 has risen too high, the controller 62 may decrease the valve position V to cause the pressure P to return below the safety pressure more quickly. Decreasing the valve position V may be referred to as adjusting the proportional valve 246 with a negative increment I (i.e., an increment I with a negative value). If so, the pressure P in the low vacuum region 22 is less than the safety pressure, then the process proceeds to step 348.

[0044] At step 348, the controller 62 determines whether the vacuum interlock device 34 is at or below the operating pressure. In other words, the controller 62 determines whether the vacuum interlock device 34 has been fully evacuated. In one example of an embodiment, the controller 62 uses a position V of 100% (i.e., the proportional valve 246 is fully open) as a representation of whether the vacuum interlock device 34 is at the operating pressure. In other embodiments, the controller 62 may use a position V at a different percentage (e.g., 75%, 80%, etc.) as a representation of whether the vacuum interlock device 34 is at the operating pressure. In other examples of embodiments, a second pressure sensor (not shown) may be coupled to the vacuum interlock device 34. In these embodiments, the second pressure sensor is connected to the controller 62 and may send a pressure reading from within the vacuum interlock device 34 to the controller 62. The controller 62 may then use the pressure reading from the second pressure sensor to determine whether the vacuum interlock device 34 has reached the target pressure. If not, the controller 62 returns to step 324 to further incrementally open the proportional valve 246. Steps 324 to 348 are then repeated until the pressure within the vacuum interlock device 34 is less than or equal to the operating pressure.

[0045] Returning to step 320, if the controller 62 determines yes, there have been sufficient operating cycles to calculate the starting position V S, the process proceeds to step 356. At step 356, the controller 62 obtains the values of pressure P, position V, operation cycle counter C, and time counter T stored in the database 66. In the illustrated embodiment, the controller 62 obtains the values of pressure P, position V, operation cycle counter C, and time counter T stored in the database 66 from X number of operation cycles. X can be equal to any integer (e.g., 10, 20, etc.).

[0046] At step 360, the controller 62 uses the obtained values of pressure P, position V, operation cycle counter C, and time counter T to calculate the starting position V of the proportional valve 246 s . The controller 62 calculates the starting position V s , the purpose of which is to reduce the evacuation time (associated with the time counter T) while keeping the pressure in the low vacuum region 22 below the safety pressure (or adjusted safety pressure). The controller 62 can implement any suitable set of calculations to determine the proportional valve starting position V s . In an example of the embodiment, the controller 62 can analyze one or more of the stored values of pressure P, position V, operation cycle counter C, and time counter T of the cycle C. As a non-limiting example, the controller 62 can determine the valve position V when the detected pressure P is less than the safety pressure. The valve position V can be implemented as the starting position V s . Additionally, or alternatively, the controller 62 can calculate the moving average of the cycle C for the valve position V when the detected pressure P is less than the safety pressure, and implement the moving average valve position V as the starting position V s .

[0047] At step 364, the controller 62 adjusts the position V of the proportional valve 246 to the calculated starting position V s .

[0048] At step 368, the controller 62 increments the time counter T. Incrementing the time counter T indicates that the time unit has increased. Step 368 is the same as step 328. Thus, step 368 can include any of the features described with reference to step 328.

[0049] At step 372, the pressure sensor 30 measures the pressure in the low vacuum region 22. The position V of the proportional valve 246 can also be measured. Step 372 is the same as step 332. Thus, step 372 can include any of the features described with reference to step 332. After step 372, steps 336 and 376 are initiated. At step 336, the values of pressure P, position V, operation cycle counter C, and time counter T are stored in the database 66, as described in further detail above.

[0050] At step 376, when high-pressure air enters the low-vacuum region 22, the low-capacity fore pump 226 operates to reduce the pressure in the low-vacuum region 22. Step 376 is the same as step 340. Thus, step 376 can include any features described with reference to step 340.

[0051] At step 380, the controller 62 determines whether the pressure P in the low-vacuum region 22 is less than the safe pressure (or adjusted safe pressure). Step 380 is the same as step 344. Thus, step 380 can include any features described with reference to step 344. If not, then the pressure P in the low-vacuum region 22 has not been sufficiently reduced by the low-capacity fore pump 226, so the controller returns to step 368 to increment the time counter T. Then steps 368 to 380 are repeated until the detected pressure P in the low-vacuum region 22 is less than the safe pressure (or adjusted safe pressure). If so, then the pressure P in the low-vacuum region 22 is less than the safe pressure, and the controller 62 proceeds to step 384.

[0052] At step 384, the controller 62 determines whether the vacuum interlock device 34 is at or below the operating pressure. Step 384 is the same as step 348. Thus, step 384 can include any features described with reference to step 348. If not, then the controller 62 proceeds to step 388.

[0053] At step 388, the controller 62 incrementally opens the proportional valve 246 by an increment I. Step 388 is the same as step 324. Thus, step 388 can include any features described with reference to step 324. After step 388, the controller 62 returns to step 368 to increment the time counter T.

[0054] Returning to step 348, if so, then the controller 62 proceeds to step 392. Similarly, at step 384, if so, then the controller proceeds to step 392. At step 392, the controller 62 resets the time counter T to zero (0). Once the controller 62 resets the time counter T to zero (0), the previous time counter T value stored in the database 66 will be used as a measurement of the evacuation time for the corresponding operation cycle C. For example, before the time counter T is reset to zero (0), the last time counter T value stored in the database could be thirty (30). In this example, the evacuation time is thirty (30) time units. The controller 62 can then attempt to reduce the evacuation time during future operation cycles.

[0055] At step 396, the vacuum interlock device 34 is at or below the target pressure, and the controller 62 closes the proportional valve 246. In other words, the controller 62 adjusts the valve position V to zero (0). Once the proportional valve 246 is closed, the vacuum interlock device 34 is fluidly isolated from the remainder of the vacuum system 12. After step 396, step 312 ends. Returning to reference Figure 5 , after step 312, the controller proceeds to step 400.

[0056] Next, at step 400, once the vacuum interlock device 34 reaches the operating pressure, the high vacuum valve 38 is opened. In some embodiments where the high vacuum valve 38 is manually operated, the user may be instructed to open the vacuum valve 38, for example, via a graphical user interface. The vacuum interlock device 34 and the high vacuum valve 38 are now fluidly connected. Step 400 is the same as step 116. Thus, step 400 may include any of the features described with reference to step 116.

[0057] Next, at step 404, in response to the opening of the high vacuum valve 38, the sample 40 (or the mechanical assembly 40) travels from the vacuum interlock device 34 to the high vacuum region 18. In some embodiments, the tool 42 may be extended to place the sample 40 (or the mechanical assembly 40) within the high vacuum region 18. The sample 40 may then be ionized and tested. Step 404 is the same as step 120. Thus, step 404 may include any of the features described with reference to step 120.

[0058] The process 300 describes introducing and measuring the sample 40. It will be understood that the process 300 may alternatively be performed to complete maintenance operations (e.g., replacing the cartridge, source plug, etc. of the ion source 13). The process 300 will include similar steps using the mechanical assembly 40 in place of the sample 40. For example, during the process of replacing the cartridge of the ion source 13, at step 308, the cartridge is introduced into the vacuum interlock device 34. At step 404, the cartridge replaces the old cartridge and then mates with the ion guide.

[0059] Although the invention has been described in detail with reference to certain preferred embodiments, there are variations and modifications within the scope and spirit of one or more of the independent aspects of the invention as described. The various features and advantages of the invention are set forth in the appended claims.

Claims

1. A vacuum system for a mass spectrometer, the vacuum system comprising: First vacuum area; Second vacuum area; a vacuum interlock, the vacuum interlock being fluidly connected to the first vacuum region via a first valve, the vacuum interlock being fluidly connected to the second vacuum region via a second valve, the vacuum interlock being configured to receive a sample; a first pump fluidly connected to the first vacuum region and the second vacuum region, the first pump configured to reduce pressure within the first vacuum region and exhaust air into the second vacuum region; a second pump fluidly connected to the second vacuum region, the second pump configured to reduce the pressure within the vacuum interlock; a pressure sensor configured to determine a pressure within the second vacuum region; and A controller is configured to incrementally adjust a position of the second valve in response to the pressure within the second vacuum region, the controller being configured to prevent pressure fluctuations in the second vacuum region. 2 . The vacuum system of claim 1 , wherein the second vacuum region has a higher pressure than the first vacuum region.

3. The vacuum system of claim 1 , wherein in a first operating cycle, the controller adjusts the position of the second valve to a first predetermined initial position, the position of the second valve changing with time is stored in a memory, and the pressure of the second vacuum region changing with time is stored in the memory.

4. The vacuum system of claim 3 , wherein in a second operating cycle following the first operating cycle, the controller adjusts the position of the second valve to a second calculated initial position, the position of the second valve over time is stored in the memory, and the pressure of the second vacuum region over time is stored in the memory.

5. The vacuum system of claim 4 , wherein the controller adjusts the position of the second valve to the second calculated initial position in the second operating cycle in response to the stored position of the second valve over time and the pressure of the second vacuum region over time from the first operating cycle.

6. The vacuum system of claim 5, wherein the second calculated initial position is different from the first predetermined initial position.

7. The vacuum system of claim 5 , wherein in a third operating cycle following the first operating cycle and the second operating cycle, the controller adjusts the second valve to a third calculated initial position in response to the stored position of the second valve over time and the pressure of the second vacuum region over time from the first operating cycle and the second operating cycle.

8. The vacuum system of claim 7, wherein the third calculated initial position is different from the first predetermined initial position and the second calculated initial position.

9. The vacuum system of claim 1, wherein: In response to receiving the sample, the vacuum interlock is at a starting pressure, In response to the second valve being fully opened, the vacuum interlock is at operating pressure, and The starting pressure is greater than the operating pressure.

10. The vacuum system of claim 9, wherein an evacuation time is defined between the vacuum interlock being at the starting pressure and the vacuum interlock being at the operating pressure, and wherein the controller is configured to minimize the evacuation time.

11. The vacuum system of claim 10, wherein the first valve is opened in response to the vacuum interlock reaching the operating pressure, and wherein the operating pressure is a pressure at which the first pump safely operates.

12. The vacuum system of claim 1, wherein in response to opening the second valve, pressure within the second vacuum region increases.

13. The vacuum system of claim 12, wherein pressure fluctuations in the second vacuum region cause damage to the first pump.

14. The vacuum system of claim 1, wherein the second pump requires less than 50 watts of power.

15. The vacuum system of claim 1, wherein the controller reads the pressure of the second vacuum region at a rate of at least 5 Hz.

16. A method of evacuating a vacuum interlock in a vacuum system of a mass spectrometer, the vacuum system comprising a first vacuum region connected to the vacuum interlock by a first valve fluid, a second vacuum region connected to the vacuum interlock by a second valve fluid, a first pump that reduces pressure within the first vacuum region, and a second pump that reduces pressure within the second vacuum region, the method comprising a first operating cycle, the first operating cycle comprising: closing the first valve and the second valve to fluidly isolate the vacuum interlock from the first vacuum region and the second vacuum region; measuring the pressure within the second vacuum region; incrementally opening the second valve to reduce pressure in the vacuum interlock, the second valve incrementally opening in response to the pressure in the second vacuum region; closing the second valve in response to the vacuum interlock reaching an operating pressure; as well as The first valve is opened in response to the vacuum interlock reaching the operating pressure to facilitate transfer of at least one of a sample, an ion source cartridge, or a source plug from the vacuum interlock to the first vacuum region.

17. The method of claim 16, further comprising storing the position of the second valve over time and storing the pressure within the second vacuum region over time.

18. The method of claim 17, further comprising a second operating cycle, the second operating cycle comprising calculating an initial position in response to a stored position of the second valve over time and a stored pressure in the second vacuum region over time in the first operating cycle, and The second valve is opened to the initial position to reduce the pressure in the vacuum interlock.

19. The method of claim 18, wherein the second operating cycle comprises incrementally opening the second valve to reduce the pressure in the vacuum interlock.

20. The method according to claim 19, wherein The first operating cycle defines a first emptying time, The second operating cycle defines a second emptying time, and The second emptying time is less than the first emptying time.

Images